/**
 * 分页插件类(缺少每页的显示数，listrows明天写)
 * @param page {Number} 当前页
 * @param pagesize {Number} 每页记录数
 * @param total {Number} 总记录数
 * @constructor
 */
function Paginate(page, pagesize, total){
    if(!page || page <1){
        page = 1;
    }
    if(!pagesize || pagesize<1){
        pagesize = 20;
    }
    if(!total || total <0){
        total = 0;
    }
    this.pagesize = pagesize;
    this.total = total;
    if(this.total % this.pagesize === 0){
        this.maxpage = parseInt(this.total/this.pagesize);
    }else{
        this.maxpage = parseInt(this.total /this.pagesize) + 1;
    }
    if(page>this.maxpage){
        this.page = this.maxpage;
    }else{
        this.page = page;
    }
}
/*
* 当前开始的条数
*/
Paginate.prototype.first = function(){
    var first = (this.page-1)*this.pagesize;
    if(first>this.total){
        return (this.maxpage-1)*this.pagesize;
    }
    return first; 
}
/*
* 当前页最大的条数
*/
Paginate.prototype.last = function(){
    var last = this.first()+this.pagesize;
    if(last>this.total){
        return this.total;
    }
    return last;
}
/**
 * 上一页
 * @returns {number}
 */
Paginate.prototype.prev = function(){
    if(this.page <= 1){
        return false;
    }
    return this.page-1;
}
/**
 * 下一页
 * @returns {*}
 */
Paginate.prototype.next = function(){
    if(this.page >= this.maxpage){
        return false;
    }
    return (parseInt(this.page)+1);
}

module.exports = Paginate;

// 使用方法->后端接口
// var Paginate = require("../plugin/Paginate");
// var q = req.query.q;
// var paginate = new Paginate(q, 10, 185);
// var page = paginate.page;//当前页数
// var first = paginate.first();//当前第一条
// var last = paginate.last();//当前最大条数
// var maxpage = paginate.maxpage;//总页数    
// var pagesize = paginate.pagesize;//每页显示数
// var total = paginate.total;//总记录数
// var prev = paginate.prev();//上一条
// var next = paginate.next();//下一条 
// res.json({page:page, first:first,last:last,maxpage:maxpage,pagesize:pagesize, total:total,prev:prev,next:next})